Artificial arm hook or hand with force multiplier and lock



Feb. 6, 1951 G. Morls 2,540,375

ARTIFICIAL A HOOK OR HAND WITH FORCE MULTIPLIER AND Loox 3 Sheets-Sheet l Filed March 30, 1948 Swmwlm Feb. 6, 1951 G M Mo'rls 2,540,375

ARTIFICIAL lHOOK OR HAND WITH FORCE MULTIPLIER AND LOCK Filed March 50, 1948 5 Sheets-Shea?l 2 TTOZIYEV Feb. 6, 1951 G. M. MoTls ARTIFICIAL ARM Hoox 0R HAND WITH FORCE MULTIPLIER AND LOCK 3 Sheets-Sheet 3 Filed March' so, 1948 WEA/T02,

Iatented Feb. 195i ARTIFICIAL ARM'HOOK OR HAND WITH FORCE MULTIPLIER AND LOCK Gilbert M. Motis, Burbank, Calif., assigner to Northrop Aircraft, Inc., Hawthorne, Calif., a corporation of California Application March 30, 1948, Serial No. 17,996

'7 Claims.

The present invention relates to hooks or hands for artificial arms, and more particularly to that class of hooks or hands wherein the movable hook members or lingers are normally opened out to the extended position by light spring pressure, and are closed by the application of a control force to the actuating mechanism.

One of the most diiiicult problems in connection with the design of such hooks or hands is that of providing both a large amount`of travel for the movable gripping members so that the hook or ngers can be opened wide, and at the same time, a hi-gh mechanical advantage in the system so that a powerful grip can be obtained on the article to be grasped. rEhe actuation of the hook or fingers is usually accomplished by means of a control member, such as a Bowden cable or the like, which is connected to a shoulder harness in -a manner whereby a shrug of the shoulder produces a pull on the control member. The muscular effort available for closing the hook or ngers is rather limited, however, both in the magnitude of the force that can be applied and in the length of travel that can be obtained in the control member, and as a result, it has heretofore been necessary to settle with a compromise solution, using the maximum mechanical advantage that would still allow the hook or fingers to be fully closed with the limited travel available in the control member. the mechanical advantage of the system has necessarily been accompanied by a corresponding sacrifice in the amount of travel of the movable hook member, which is undesirable, and prior hooks or hands have therefore been characterized by a relatively weak closing action.

The primary object of the present invention is to overcome these diiiiculties by providing a hook or hand combining the desirable characteristics of a high mechanical advantage with a large amount of angular travel of the movable,

gripping member. This has been accomplished by providing means whereby the movable gripping member is closed with a fast motion and low mechanical advantage during the no-load portion of its travel while moving from the fully opened position up to the point of its engagement with the article to be grasped, and then changes automatically to a condition giving a slow travel and high mechanical advantage while tightening its grip on the article.

Another object of the invention is to provide a hook or hand of the manually closed type wherein the movable gripping member is automatically locked in the closed position when the Any attempt to increase d force exerted by the control member is released, thereby enabling the amputee to relax the harnessed shoulder while still maintaining his grasp on the article.

A further object of the invention is to provide a self-locking hook or hand of the class described, having means operable by the next succeeding pull on the control member to release the lock, permitting the movable gripping member to be opened.

Still another object of theinvention is to provide a manually closed, self-locking hook or hand embodying yielclable spring means in the actuating mechanism which is adapted to be stressed at the time the movable gripping member is tightened up on the article, so that when the tension in the control member is released and the gripping member is locked in closed position, the stressed spring means applies a force back into the actuating mechanism, causing the movable gripping member to exert a substantial spring pressure on the article held thereby. This is an important feature when handling hard, unyelding objects, since without such spring action, it would be impossible to maintain the necessary firm grip on the article except by sustained` muscular effort.

The foregoing and other objects and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of two illustrativel embodiments thereof, reference being had to the accompanying drawings, wherein:

Figure 1 is a perspective view of a hook embodying the principles of the invention;

Figure 2 is a top plan View of the same;

Figure 3 is a View similar to Figure 2, showing the 'movable hook member closed 'on an object, with the actuating mechanism depicted in the condition giving a fast motion with low mechan` ical advantage, as during the initial no-loacl travel of the hook;

Figure 4 is an enlarged, partially sectioned, pian view of the actuating mechanism, showing the positions of the several parts thereof when the mechanism isin the condition giving slow motion with high mechanical advantage, as when the movable hook member is being drawn tight on the object; l

Figure 5 shows the actuating mechanism in the locked position which is assumed when the force exerted by the control member is relaxed;

Figure 6 shows the manner in which the lock is released when the next succeeding force is applied to the control member;

Figure 1 shows the actuating mechanism in the final phase of the operational cycle, during which the control member is being relaxed to open the hook, and the locking pawl is being cammed down to the point at which the associated spring and link are caused to snap over center to their initial position, in readiness for the next cycle of operation; and

Figure 8 is a perspective view of an artificial hand embodying the principles of the invention in the finger-closing mechanism.

Reference is had iirst to Figures l to 7, inclusive, of the drawings, wherein the numeral l designates the forearm component of Yan artificial arm, the outer end of which terminates in a wrist cap I I, having an attach plate I2 mounted thereon in any suitable manner. The outer face of the attach plate I2 is milled out to form a sha1-'- low, vertically extending slot I3 having grooves I4 cut into the opposite side walls thereof. The slot I3 is open at the top and is adapted to receive a companionate rib I5 formed on the back side of the base I5 of a hook unit I1, providing a quick-detachable coupling for connecting the hook unit onto the arm. The rib I5 has flanges 20 projecting from its opposite side edges, and these flanges are adapted to slide endwise down into the grooves I4 in the attach plate. A locking pin 2l which is slidably disposed within a hole in the base i6 near the top edge thereof, is urged rearwardly by a cantilever spring 22, and is adapted to drop into a hole in the face of the attach plate i2 when the hook unit is fully seated thereon, to lock the hook unit in place.

The attach plate I2 may be rotatably mounted on the cap II, or it may be stationary with respect thereto, and since the details of the connections between them form no part of the present invention, they have accordingly been omitted from the drawings. A centrally disposed tubular extension 23 projects rearwardly from the back of the attach plate l2 through an opening in the cap l I, and slidable axially within the bore 24 thereof is a cylindrical coupling member 25. The bore 2d extends through the plate I2 and opens at its front end into the bottom of the slot I3. A spring 2S bears against the back end of the member 25, urging it outwardly, or to the left, as shown in the drawings. Attached vto the coupling member 25 in any suitable manner is the tensionftransmitting wire 30 of a Bowden cable control. The Bowden cable includes the usual flexible, spring-wound conduit `(not shown) which encloses the wire 35 for a substantial portion of its length, said wire being freely slidable within the conduit. The conduit and wire extend upwardly along the length of the arm, and the upper end of the wire is attached to the usual shoulder harness (not shown), which is constructed and arranged so that a shrug of the shoulder produces a pull in the wire 35, in a manner well understood in the art.

The outer end of the coupling member 25 is adapted to project beyond the bottom surface of the slot I3, and is milled out to form a T-shaped slot 3| which is open at the top side of the coupling member so as to receive a circular, radially iianged connector 32 projecting from the back of the base I5, when the hook unit I1 is inserted down into the slot I3. The connector 32 is connected to actuating mechanism 33 of the hook unit, and, when coupled to the member V25, serves to transmit the pull of the control wire 3B to the actuating mechanism to operate the same. Since the connector 32 is the means by which the actuating mechanism is operated, it might be considf which protects the mechanism and prevents the clothing from becoming entangled therein. The housing 29 may be attached to the base plate I6 in any convenient manner, and is provided with suitable openings through which the two cooperating hook members project. Another opening in the top of the housing 29 permits a handle extension 28 on the wire spring 22 to project through to the outside so that it can be grasped by the fingers of the other hand to unseat the pin 2l from its hole in the attach plate I2, and thereby unlock the hook unit I1 for removal therefrom.

The base plate I6 of the hook unit is shaped to conform to the outline of the attach plate I2, and is apertured centrally to provide an opening 34 which receives the connector 32. Projecting forwardly from one side of the base plate I6 is a post 35 which terminates at its outer end in a cylindrical extremity 36 having a threaded socket 31 formed therein. The threaded stud 45 of a stationary hook member 4I is screwed into the socket 31. On the other side of the centerline of the plate I6 from the post 35 are two vertically spaced, outwardly projecting lugs 42 which are apertured at their outer ends to receive a pivot bolt 43. Disposed between the lugs 42 and journalled on the pivot bolt 43 is a bell crank member 44, one arm of which extends in a generally outward direction and terminates in a cylindrical extremity 45 having a threaded socket 46 to receive the stud 41 of a movable hook member 5I. Both the stationary hook member 4I andthe movable hook member 5l are preferably covered for the greater portion of their lengths by pieces of rubber tubing 49 which provide a good frictional surface for the hooks, as well as a slight amount of elastic yield, or cushion, to facilitate handling smooth or hard objects. The other arm of the bell crank member 44 is bifurcated, forming two spaced arm portions 52 which extend laterally in the general direction of the post 35. rl`he outer ends of the arm portions 52 are drilled to receive a pivot pin 53.

Disposed between the arm portions 52 and journalled on the pin 53 is an operating lever 5d, the longer arm of which extends laterally inward toward the axis of the pivot bolt 43. This inwardly extending arm of the operating lever 54 is bifurcated, being slotted out lengthwise to form a shoulder at 55 adjacent the pivot pin 53. Disposed between the side portions of the operating lever '54 adjacent the free end thereof and pivotally connected thereto by a pin 55 is an L-shaped link 60, the other end of'which extends into a slot in the connector 32, and is secured by a pin 6I. 'The attach plate I6 is slotted out at 62 between the lugs 42 to provide clearance for the link 60.

The outer end Aof the operating lever 54 projects radially outward beyond the pivot 53 and is provided with a toothed sector 65 which is engageable with the teeth of an arcuate rack 65 mounted on the post 35, when the operating lever is rocked in a counterclockwise direction. Formed in the front outer corner of the operating lever 54 is a notch lil, and seated therein is one end of a bowed, U-shaped spring 1|, the other end `of which is engaged in a notch 'I2 in the bell crank member 44. The spring 'Il exerts a pressure on the operating lever 54 tending to rotate the same in a clockwise direction so as to move 'the toothed sector 65 out of engagement with the rack 66. Opposing this clockwise torque is a counterclockwise torque which is produced in the operating lever by the pull of the control Wire 36, acting through the coupled members 25, 32, and link Eil, The force exerted on the operating lever by the spring l I is somewhat greater than the torque which must be applied thereon by the hook-closing control force at point 56 to overcome the light spring pressure urging the movable hook member to the open position. The spring pressure referred to is exerted by a pair of cantilever springs 'i3' disposed on opposite sides of the hook members. Preferably, the springs 13 are formed of spring steel wire, each -being bent to an angle at one end, as at 14, and inserted into a snug-tting hole in the attach plate IB for anchorage. The other end of each of thesprings bears downwardly against and is slidable over a pin i5 projecting laterally from both sides of the bell crank member 44. Since pin 15, which is the point of application of the force exerted by springs i3, is located below the axis of pivot 43, it will be seen that the bell crank member 44 and associated hook member 5I are urged in a counterclockwise direction, away from the stationary hook member 4i. Counterclockwise rotation of the member 44 causes the link Gli and connector 32 to be drawn toward the left, as viewed in the drawings, and the angular travel of the member` 44 is limited at the fully opened position of the hooks by the engagement of a flange 16 on the connector 32 with an annular shoulder 'H in the opening 34.

From the foregoing, it will be seen that the only force to be overcome during the initial no-load travel of the members 44, 5 i is the torsional force exerted thereon by the two cantilever springs 13. Since the torque applied'to the operating lever 54 by spring 'H exceeds the torque which must be applied thereto by the control force to overcome the torsional force of the springs 13, the operating lever remains stationary with respect to the arm 52 during the no-load travel of the movable hook member 5i, and the effect is the same as though the link 6D were connected directly to the arm 52 at point 56. ATit will be noted that the moment arm between the point of force application at pin 56 and the axis of pivot 43 is relatively short, and as a result, a relatively large angular travel is obtained in the bell crank member ifi with a relatively small linear travel of the control Wire 30 and coupled members 25, 32. While the torque applied to the members 44, 5I by the control force acting directly on point 55 is sufficient to overcome the hook-opening force of springs 73, the adverse mechanical advantage of the system due to the relatively long moment arm from the axis of pivot 43 to the outer end of the movable hook member 5I makes it impossible to apply any effective pressure on an object A (Figure 3) held between the outer ends of the hook. Accordingly, when the movable hook member has closed solidly against the object, and further travel is resisted thereby, the actuating mechanism 33 goes into operation to change the force transmission system over toa condition giving a Ahigh mechanical advantage. This sec.-`

' ond phase `of the operating cycle, illustrated in Figure 4, will now be described.

As the movable hook member 5| meets the resistance of the object A and is brought to a stop, the amount of muscular force applied to the control wire 30 through the shoulder harness is voluntarily increased, producing an increased counterclockwise torque in the operating lever 54 which presently overcomes the torque of the spring 'l l. With the overpowering of the spring 1|, the operating lever 54 is rocked in a counterclockwise direction about the pivot pin 53, bringing the teeth of the sector 65 into engagement operating lever 54 becomes a fulcrumed lever arm,

wherein the point of engagement of the sector teeth 65 with the rack 66 constitutes the fulcrum point; pin 53 being the load; and pin 55, of course, representing the point of application of the force. In the embodiment illustrated in the drawing, the length of the lever arm from the center of pin 53 to the center of pin 5E is roughly three times the length of 'the lever arm from pin 53 to the pitch line of the intermeshed teeth; hence the actuating force (load) applied at 53 is approximately three times as great as the control force applied at 5S. AV second factor which must also be considered is the fact that the control force is now applied to the bell crank arm 52 at the pin 53, instead of at the pin 56. The moment arm of pin 53 with respect to the ax of the bell crank pivot 43 is about four times as great as that oi' the pin 55, and this four-to-one leverage ratio gives a total force multiplication in the system of approximately twelve-to-one over that which was obtained before the operating lever 54 was rocked to engage the teeth 65 with the rack t. that the above ratios and proportions are merely illustrative, and might be varied widely without departing from the scope of the invention.

rEhe arcuate rack t is preferably formed separate from the post 35 and is slidably mounted on an arcuate face Si] thereof, the center of curvature of which lies at the axis of the bell crank pivot 43. The teeth of the rack 65 extend only about half way across the width thereof, leaving a smooth strip it extending alongside the toothed portion. The rack is secured to the face 86 by two rivets Si which extend through circumferentially elongated slots 32 in the smooth portion "i9 of the rack, permitting a limited amount of sliding movement of the latter with respect to the post within the limits of the slots. rlhe rack 6% is urged toward the right, as viewed in the drawings, by a bowed leaf spring 83, one end of which is lodged under a pin t4 projecting from the post S5 adjacent the outer end of the rack, and the other end of said spring being engaged in a notch 35 in the smooth portion "ifi of the rack at the farend thereof. ,The spring 83 is fairly substantial, and exerts a pressure of about 50 pounds on the rack Et, the purpose of which will become apparent hereinafter.

When the movable hook member 5l has been drawn up tight to the desired pressure against the object A, the force on the control wire 3d is voluntarily relaxed, causing the actuating mechanism 33 to assume a locked holding condition, illustrated in Figure 5. The locking action is accomplished by a generally U-shaped locking pawl Sii, one end of which is formed with a pointed, wedge-shaped lip il@ which is adapted to ratchet over and engage any one of the inclined teeth of an arcuate rack SI'. The rack 9i isformed t will be understood, of course,-

integral with the bell crank member 44 and projects laterally therefrom in the general direction of the post 35. The center of curvature of the line of teeth on the rack 9| is preferably, a1- though not necessarily, located at the center of the pivot 53 for the operating lever 54.

The pawl 8S extends through the slot in the operating lever 54 and is pivotally connected at its other end by a pin S2 to a link 93. The link 93 is also disposed between the sides of the slotted operating lever 54 and is pivot-,ally connected thereto intermediate its ends by a pin t4. The other end of the link 93 projects beyond the pivot 94 and is provided with a notch 95 which engages one end of a bowed leaf spring 95. The other end of the spring 95 is seated in a notch 91 formed in the back of the wedge-shaped lip 90 of the pawl 8e. The link 93 is limited in its angular travel about the pivot 94 by two pins 98 and 99 which extend through alined holes in the side portions of the slotted operating lever 54. The link is shown in its extreme clockwise position in Figure fi, and in its counterclockwiselimited position in Figure 5. The notch 95 is located so that when the link is in its clockwise position, the notch lies above a centerline drawn through the notch 9? and the center of pivot 94; and when the link is in its counterclockwise position, the notch lies below the said centerline` With the parts shown in the relative positions occupied in Figure 4, the spring St exerts a force on the free end of the pawl 85, urging the lip 9S downwardly against the teeth of rack 53|. This is the initial condition of the linkage at the time the closing operation of the hook is iirst started.

1t might be noted at this point that there is a notch W9 formed in the rack 9| adjacent the outer end thereof, and beyond the notch is a tongue Iii! having an inclined cam face |62. The lip 96 of the pawl is normally seated in the notch |09 when the hook is at rest. During the tightening phase or" the operation, described earlier, the counterclockwise rocking movement of the operating lever 54 with respect to the bell crank arm 52 causes the link pivot 94 to move toward the right in an arcuate path about the operating lever pivot 53 as a center. Since the .pawl 36 is supported on the operating lever through the medium of the link 93, this movement toward the right of the operating lever carries the pawl along with it, lifting the lip d out of the notch i9@ and causing the lip to ratchet over the teeth of the pawl. When the force on the control wire 3U is relaxed, the lip 9e on the pawl drops into locking engagement with the last tooth passed over, and the pawl is thereby prevented from moving back toward the outer end of the rack.

As the hook is drawn up tight on the object A, the reaction of the toothed sector S on the arcuate rack 56 causes the latter to be pushed outwardly, or to the left, against the pressure of the leaf spring 83, In Figure cl, the rack is shown at the extreme left hand position. With the release of the tension in the control wire 30, the rack is pushed back slightly by the stressed spring 83, to a position somewhere between its extreme positions, as shown in Figure 5, carrying the toothed sector S5 with it. Since the bell crank member 44 and movable hook member 5i are limited against further clockwise rotation by their engagement with the unyielding object A, the pivot 53 remains stationary, and the operating lever 54 therefore tends to rock in a clockwise direction about the pivot .53. However, in order for the .lever 54.

operating lever 54 to rotate clockwise from its position in Figure 4, it is necessary also for the pivot pin 94 to move toward the left in an arcuate 4path about the axis of the pivot 53 as a center, but such movement of the pin 94 is resisted by the spring-pressed link B3 and pawl 86, which are connected thereto. The pawl 85, being engaged with the rack Q is prevented from moving toward the left; and the pin 92, which might also be considered a part of the pawl, is likewise prevented from moving toward the left. Hence, the only movement of which link 93 is capable is clockwise rotation about the pivot 92.

With the linkage in the position shown in Figure 4, the pin 94 lies slightly above the bottom oi its arcuate path about the pin 92; the bottom being considered las the point at which a line drawn through the centers of the pins 53 and 94 is tangent to the circular path of the pin 94 about the pin 92. Accordingly, a force toward the left, applied by the operating lever 5t to the pin gli, causes the latter to ride down its arcuate path about the pin 92 until the notch 55 passes a centerline drawn through the notch and pin 94. When this happens, thespring St snaps the link 93 down to the counterclockwise position limited by pin 99, as shown in Figure 5, and spring 5t now exerts a `force on the outer end of the pawl tending to urge the same away from the rack Si The lip 96 of the pawl is held by the tooth of the rack, however, and is thus prevented from moving away from the latter.

From the foregoing explanation, it will be seen that the spring acting on the sliding rack BB, exerts a'spring force back through the actuating system when the latter is locked, causing a spring pressure to be exerted on the object A by the movable hook member'i when the control force has been relaxed and the mechanism is locked. When in the locked condition just described, the actuating mechanism 33 is relatively immovable, and the lforce of the spring S3 is, in eiiect, applied directly to the bell crank 44 at a moment arm equal to the Vdistance between the center of the pivot 43 and the pitch line of the teeth in the rack. Since this moment arm is about one-fourth of the moment arm of the movable hook member 5|, measured from the pivot 43 to the object A, a fty-pound force exerted by spring 83 on the rack 66 results in a twelve and one-half pound pressure by member 5I on the object A. This is considered adequate for most purposes.

The next step in the operating cycle might be termed the unlocking step, and this is shown in Figure 6. When the amputee wishes to release the object A, he shrugs the harnessed shoulder again, applying another force to the control wire 30, which exerts a counterclockwise torque on the operating lever 54. Again, since the bell crank member 44 and movable hook member 5i are limited against further clockwise rotation by their engagement with the unyielding object A, the only relative movement possible in the system is counterclockwise rotation of the operating lever 54 with respect to the bell crank member, which is permitted by virtue of the sliding movement of rack 58 against the pressure of spring'83. This limited rotation of the operating lever causes the lip'Bi of the pawl Se to be lifted clear of the teeth of -rack 9|, so that the spring 9B is enabled to Vsnap the pawl up to the position shown in Figure 6. Upward -movement of the pawl is limited by its engagement-with the shoulder 55 at the bottom oi vthe slot in the operating 'Ihe locking pawl 86, being now disengaged from the rack 9|, no longer prevents clockwise rotation of the operating lever 54, and the lever is accordingly rocked in a clockwise direction by the spring TI until the toothed sector 65 disengages and clears the teeth of the rack 66. The movable hook memberl and bell crank 44 are then returned to their open position by the cantilever springs '|3.

In the final phase of the operating cycle, the locking pawl 86 is reset to its initial condition, with the lip 99 seated in the notch Iliil and urged by the spring S6 down toward the teeth of the rack 3|, This occurs as the several parts of the actuating mechanism approach their normal positions of rest, and is shown in Figure '7. Clockwise rotation of the operating lever 54 under the urging of spring 'Il carries the pawl 86 around to the left so that the lin 93 thereof engages the cam face |02. The final portion of the angular movement of the operating lever with respect to the bell crank arms 52 causes the lip 90 to be cammed down into the notch I im, and at the same time` forces the pin 92 to ride down its arcuate path about pin 94 as a center, until the notch 95 passes above the centerline drawn through notch 97 and pin 94. The spring 96 then snaps the link 93 up to its clockwise limited position, and the mechanism is now reset to its initial condition, in readiness for the next cycle of operation.

Those skilled in the art will readily appreciate the many advantageous features of the hook described hereinbefore. The fast-motion, lowmechanical-advantage prevailing in the system during the initial no-load closing movement of the hook enables the hook to be closed rapidly with a minimum of muscular effort at the harnessed shoulder. When the hook has closed on the object and a high mechanical advantage becomes desirable for the purpose of obtaining a firm grip on the object, the mechanism shifts automatically to a slow-travel, high-mechanicaladvantage condition. The self-locking feature, with spring pressure applied to the movable hook member `when the actuating mechanism is locked, Y

and the provision of means for unlocking the mechanism. responsive to the next succeeding application of force to the control wire 30, will likewise be recognized as important advantages.

Another highly desirable feature of the invention is the fact that the spring 83 allows thel arcuate rack 56 to yield slightly under excessive loads, which permits the hook 5| to open sufciently to release its grip in an emergency. This f prevents injurious shock loads from being trans- The hand is designated in its entirety by the reference numeral Ht, and comprises a base III having coupling lianges 2M on the back side thereof which are adapted to be engaged in the companionate grooves of the attach plate. The main body portion of the hand may be formed as a thin-walled shell I I2 of aluminum or other light Weight material, which is attached in any suitable manner to the base III around the periphery thereof. The shell ||2 is preferably divided into front and back halves for convenience of manufacture; the front half being removed in the drawing to show the mechanism in the interior.

At the outer end of the hand are movable iingers |I3, |I4, |I5 and IIE, each of which is jointed intermediate its ends for articulation. The proximal ends of lingers I|3 and H4 are l'ixedly mounted on a transverse shaft |20 which is rotatably supported on the back half of the shell I|2 by suitable bearings (not shown). The proximal end of nger I 5 is fixedly mounted on another shaft I 2| coaxial with shaft |20, and the forenger IIS is rotatably mounted on the shaft |20 for independent movement with respect thereto. Shaft |2| is rotatably supported in suitable bearings (not shown) and is coupled to shaft |20 by a friction clutch |22. lFingers I|5 and H6 are manually closed by the actuating mechanism 33a, through the agency of a linkage system which will be described presently; :while the outer two ngers H3 and ||4 are closed by the torque transmitted to shaft E26 through the friction clutch |22. Thus, the principal gripping force applied by the lingers to an object held in the hand is that exerted by fingers I I5 and IIB, and the force exerted by lingers IIS, 4 is relatively insignilicant, being limited by the torque capacity of the clutch |22. Projecting from the proximal ends of the iingers H5, IIB are ears |23 and |24, to which links |25 and |26 are connected. The links |25 and |26 are pivotally connected to opposite ends of a transversely disposed equalizer bar I 3s, and the latter is connected at its midpoint to a link |3I. The link |3| is connected, in turn, to a bifurcated lever arm |32 which is fixed on a shaft |33. The shaft |33 is journaled in a bracket |34 mounted on the back half of the shell H2, and one end of the shaft projects laterally beyond the bracket and has an arm |35 fixed thereto. Pivotally connected at |36 to the outer end of the arm |35 is a link |40, the lower end of which is provided with a yoke |39 that passes down over the outer sides of both of the arm portions 52a of the bell crank member 44a. In this embodiment, the pin 53a projects beyond the arms 52d and its ends are received within aligned holes in the yoke |39. The actuating mechanism 33a is substantially the same as that in the preceding embodiment, with the exception of the bell crank member 44a which terminates just beyond the notch 72a that anchors the spring Ha. The connector 32a (referred to in the claims as the control member) is connected by a link ct to one end of an operating lever 54a which is pivoted at 53a on the arms 52a of the bell crank member 4de. At the outer end of the, operating lever 54a is a toothed sector a. which is adapted to mesh with an arcuate rack 66a that is slidably mounted on a curved face a of a post 35a. AS in the prior example,

the rack 36a is urged downwardly by a bowed leaf spring 83a, and the toothed sector 65a is urgedout of engagement with the teeth of rack 66a by a spring lia. A locking pawl lta is connected` with the operating lever 54a by a link (not shown) similar to the link 93 of the hook actuatingmechanism 33, and the wedge-shaped lips a of the pawl is engageable with an arcuate rack 9|a.- A bowed leaf spring `95a is seated at one end in a notch in the pawl tta, and at the other end engages the link corresponding to 93,

ll to urge the same to one or the other of twofpositions, asdescribed earlier.

The action of the operating rnecl'ianisnr33a is identical to that of the previous example. When the hand is mounted on the attach plate at the write of an artificial arm', the connector1 32a is connected to the coupling member 25 at the end of the Bowden cable control'wire 313, anda shrug of the harnessed shoulder causes a pull to be applied to the member 32a. The force exerted on the member 32a'is transmitted by link Eilato the operating lever 54a and bell crank 44a. As long as the force required to rock the bell crank Mc about its pivot 43a, against the pressure of springs 'i3d is less thanA the force exerted by spring lia against the sector 65a, the operating lever 5ta remains stationary withzrespect to the bell crank Ma, andv the latter rocks, on its pivot 43uas though connected directly tothe link 6ta; This gives the fast-motion, low-mechanical-advantage action during the rio-load, portion of the bell crankstravel. When the. load on the bell crank Ma is increased` to the point where thespring 'ila is overcome, the toothed sector 65a engages the rack 66a, and the lever 54a thereafter functions as a fulcrumed lever, giving the system` a. slowtravel and high-mechanical-advantage action, whereby the fingers are enabled to close with a powerful grip on any object held thereby.

The actuating mechanism 33a is operatively connected tothe fingers by the yoke |39 andY its associated linkage. As the cuter ends of the bell crank arms 52a swing downwardly, the yoke |39 and link |4'are pulled down with it, rocking. the shaft |33 and causing the outer end of the lever arm |32 to swing downwardly. This pulls the link l3| downwardly, which causes the equalizer bar |39 to exert anequalized pull on both of the links |25, |26. Link |25,- being connected.v to finger I| which is xedly mounted on the shaft l2 l, causes the said finger to close and the shaft to rotate.v Link |26, which is connected to finger H6, causes the latter to close at the same rate as finger |15 as long asthere is no load, or the load is equally distributed between them. Since shaft IZB is connected to shaft |2| by the friction clutch |22, fingers I3 and i4 are likewise closed in unison with fingers ||5 and IIB as long as there is no load on any of the fingers. However, if either of ngers ||5or IIB is loaded more than the other, the equalizer bar |30 enables the fingers to move relative to one another until the load is equalized; such relative movement being permitted by virtue of the pivotal connection of finger H6 to the shaft i 2|. Fingers ||3andv I4 are permitted to yield under load by the slippage of clutch |22 when the torqueV capacityl of the latter is exceeded.

The distal ends'of fingers H3, H4, H5, and H6 may be connected to the back shell H2 of the hand by cross-over links |45 in a manner well known in the art, so that the fingers are flexed at the same time that they are closed.

The thumb |46 may be of any desired construction, and may be either passively positioned, as in the case ofthe illustrated hand, or manually operated. For the sake of simplicity, I have shown a rigid, one-piece thumb |46 that is pivoted at |41 on a bifurcated bracket |43 projecting radially from a turn-table |5ll. The turn-table |59 is rotatably connected by a pinV |5| to a ledge |52 that extends laterally from the back side of the post 35a. Suitable friction means may be interposed between the thumb |46 and bracketv |48, and between the turn-table 15uA and 12 ledge |52, to provide a certain amount of resistance to angular movement about each of the pivots- |41 and I`5|.

From the foregoing, it will be seen that the prinicples of the invention can be utilized with equal advantage in either a hand or hook, the only differences being in the manner of transmitting the output force of the actuating system to the movable gripping members. In the one instance, the gripping member is simply a pivoted hook; whereas in the other case, the gripping membersV consist of a plurality of individually movable nngers which are connected together to moveA in unison. The actuating mechanism 33a might'also be utilized in any other form' of hook orhand mechanism, and is not limited to the specieV constructions shown.

While I have shown and described in considerable detailV what I believe to be the preferred form of my invention, it is to be understood that such details are not restrictive, and that various changes may be made in the shape and arrangement of the several parts without departing from the scope of the invention, as defined in the appended claims.

I claim:

l. In an artificial hand or hook having a movable gripping member, actuating means connected to said gripping member to operate the same, said actuating means including a pivoted member having an arm projecting radially from its axis of rotation, an operating lever pivoted on the outer end of said arm and extending inwardly toward said axis, said operating lever being engageable with a substantially stationary element when rocked in one direction, a spring urging said operating lever in the other direction for holding the same out of engagement with said stationary element,v a control member connected to said operating lever in amanner whereby the application of a force by the control member tends to rock the operating lever in said one direction against the pressure of said spring, said movable gripping member being closed with a fast travel and low mechanical advantage as long as the torque on said operating lever due to the pressure of said spring exceeds the torque due to the force exerted by said control member, and when the torque due to the force of said control member exceeds the torque due to said spring, said operating lever is rocked into engagement with said stationary element, giving a fulcrumed lever action on the outer end of said arm, whereby said movable gripping member is thereafter closed with a slow travel and high mechanical advantage, a link pivoted intermediate its ends on said operating lever, stops for limiting the angular movement of said link between a rst position and a` second position, a locking pawl connected to one end of said link and extending around to the opposite side of the pivot point thereof, an arcuate rack projecting laterally from said movable hook member, said rack being engageable by the free end of said pawl, a spring bearing against the other end of said link and against the free end of said pawl, said last-named spring ybeing operative to urge said free end of the pawl into engagement with said rack when said link is in said first position, and out of engagement therewith when said link is in said second position, said link being initially disposed in said first position while said movable gripping member is being drawn tight on an object, whereby said pawl is ratcheted over said rack and engages one ofv the teeth thereof when 13 the force exerted by said control member is relaxed, said pawl and said link thereafter holding said operating lever in the position occupied by the latter when said control member was relaxed, whereby said movable gripping member is locked in closed position, said link being moved to said second position when said control member is relaxed, whereby the next succeeding application 4 of force by said control member causes said pawl to be lifted out of its seating engagement with said rack, allowing said last-named spring to move said pawl clear of the rack and releasing said operating lever, said operating lever Abeing moved out of engagement with said stationary element by said iirst-named spring, permitting `said movable gripping member to open, and

means engageable by said pawl for moving the same in a direction to cause said link to return to said first position.

2, In an artiiicial hand or hook having a base and a movable gripping member, actuating means connected to said gripping member to operate the same, said actuating means including a pivoted member having an arm projecting radially from its axis of rotation, an operating lever pivoted on the outer end oi said arm and extending inwardly toward said axis, said operating lever having a toothed sector projecting outwardly from its pivot support, an arcuate rack mounted on said base and engageable by said toothed sector, said rack having its center of curvature on said axis of said pivoted member, a force-transmitting control member connected to said operating levery spring means connected to said operating lever to apply a torque thereto opposing the torque exerted by said control member, said spring means being operable to hold said toothed sector normally out of engagement with said arcuate rack, whereby said movable gripping member is closed with a vlast travel and low mechanical advantage by virtue of the direct application of force of said control member to said arm as long as the torque of said spring means on said operating lever exceeds the torque of said control member thereon, and when the torque on said operating lever produced by said control member exceeds the torque produced by said spring means, said toothed sector is moved into engagement with said arcuate rack, giving a fulcrumed lever action on the outer end of said arm, whereby said movable gripping member is thereafter closed with a slow travel and high mechanical advantage, an arcuate rack mounted on said pivoted member, a locking pawl supported at one end on said operating lever and engageable at the other end with said last-named arcuate rack to hold the operating lever in its position of maximum deilection when the pull on said control member is relaxed, a spring having one end engaging said other end of said pawl, and means acting on the other end of said` spring to move the same alternately from one to the other of two positions each time said control member is operated, said spring being operable to urge said pawl into engagement with said last-named arcuate rack when said other end thereof is at one of said two positions, and to urge the pawl out of engagement with the arcuate rack when at the other of said two positions.

3. In an articial hand or hook having a base and a movable gripping member, actuating means connected to said gripping member to operate the same, said actuating means including a pivoted member having an arm projecting radially from its axis of rotation, an operating lever pivoted on the outer end of said arm and extending inwardly toward said axis, said operating lever having a toothed sector projecting outwardly from its pivot support, an arcuate rack mounted on said base and engageable by said toothed sector, said rack having its center of curvature on said axis of said pivoted member, a force-transmitting control member connected to said operating lever, a spring connected to said operating lever to apply. a torque thereto opposing the torque exerted by said control member, said spring being operable to hold said toothed sector normally out of engagement with said arcuate rack, whereby said movable gripping member is closed with a fast travel and low mechanical advantage by virtue of the direct application of force of said control member to said arm as long as the torque of said spring on said operating lever exceeds the torque of said control member thereon, and when the torque on said operating lever produced by said control member exceeds the torque produced by said spring, said toothed sector is moved into engagement with said arcuate rack, giving a fulcrumed lever action on the outer end of said arm, whereby said movable gripping member is thereafter closed with a slow travel and high mechanical advantage, and releasable locking means operatively connected to said actuating means `for locking said movable gripping member in closed position when the force exerted by said control member is relaxed, said locking means comprising a link pivoted intermediate its lends on said operating lever, a locking pawl pivoted on one end of said link and extending around to the opposite side of the pivot axis thereof, a rack on said pivoted member engageable by the free end of said pawl, and a spring bearing against the other end of said link and against the free end of said locking pawl, said link being operable to move said spring alternately between a position wherein the pawl is urged into engagement with said rack and another position wherein the pawl is urged away from said rack.

4. In an articial hand or hook having a base and a movable gripping member, actuating means connected to said gripping member to operate the same, said actuating means includinga pivoted member having an arm projecting radially from its axis of rotation, an operating lever pivoted on the outer end of said arm and extending inwardly toward said axis, said operating lever having a toothed sector projecting outwardly from its pivot support, an arcuate rack mounted on said base for limited sliding movement along its arc of curvature and engageable by said toothed sector, said rack having its center of curvature on said axis of said pivoted member, a spring acting on said rack to urge the same in one direction to the extremity of its travel, a force-transmitting control member connected to said operating lever, another spring connected to said operating lever to apply a torque thereto opposing' the torque exerted by said control member, said last-named spring being operable t0 hold said toothed sector normally out of engagement with said arcuate rack, whereby said movable gripping member is closed with a fast travel and low mechanical advantage by virtue of the direct application of force of said control member to said arm as long as the torque 0f said last-named spring on said operating lever exceeds the torque of said control member thereon, and when the torque on said operating lever produced by said control member exceeds the torque produced by said spring, said toothed sector is moved into engagement with said arcuate racky giving a fulcrumed lever action on the outer end of said arm, whereby said movable gripping member is there-- after closed with a slow travel and high mechanical advantage, said toothed sector being operative to move said arcuate rack in the direction against the pressure of said rst-named spring, thereby causing the spring to be compressed, and locking means connected to said operating lever for holding the same in the position of maximum deection when the `force exerted bysaid control member is relaxed, whereby said movable gripping member is locked in closed position, the pressure of said iirst-named spring against said arcuate rack acting on said arm of said pivoted member through the toothed sector of said operating lever to cause said movable gripping member to exert a spring-pressure on the article gripped thereby.

5. In an artificial hand or hook having a base and a movable gripping member, actuating means connected to said gripping member to operate the saine, said actuating means including a pivoted member having an arm projecting radially from its axis of rotation, an operating lever pivoted on the outer end of said arm and extending inwardly toward said axis, said operating lever having a toothed sector projecting outwardly from its pivot support, an arcuate rack having its center of curvature on said axis of said pivoted member, said rack being mounted on said base for limited sliding movement along its arc of curvature, and being engageable by said toothed sector, a Spring acting on said rack to urge the same in one direction to the extremity of its travel, a control member connected to said operating lever, another spring connected to said operating lever to apply a torque thereto opposing the torque exerted by said control member, said last-named spring being operable to hold said toothed sector normally out oi engagement with said arcuate rack, whereby said movable gripping member is closed with a fast travel and low mechanical advantage by virtue of the direct application of force of said control member to said arm as long as the torque of said last-named spring on said operating lever exceeds the torque of said control member thereon, and when the torque on said operating lever produced by said control member exceeds the torque produced by said spring, said toothed sector is moved into engagement with said arcuate rack, giving a fulcrumed lever action on the outer end of said arm, whereby said movable gripping member is thereafter closed with a slow travel and high mechanical advantage, said toothed sector being operative to move said arcuate rack in the other direction against the pressure of said rst-named spring causing said spring to be compressed, means responsive to the relaxation of the force exerted by said control member for locking said operating lever against angular movement with respect to said arm, whereby said movable gripping member is locked in the closed position, the pressure of said iirst-named spring against said arcuate rack acting on said arm of said pivoted member through the toothed sector of said operating lever to cause said movable gripping member to exert a spring-pressure on the article gripped thereby when the force exerted by said control member is fully relaxed, and means responsive to the next succeeding application of force by said control member for releasing said 16 locking means to permit said movable gripping member to open.

6. An artificial arm hook comprising a base having a stationary hook member rigidly iixed thereto, a movable hook member pivoted on said base for swinging movement toward and away from said stationary mem-ber, actuating means including an arm projecting radially from said movable hook member adjacent the axis of rotation thereof, an operating lever pivoted on the cuter end of said arm and extending inwardly toward said axis, said operating lever being engageable with a substantially stationary element on said vbase when rocked in one direction, a spring urging said operating lever in the other direction for holding the same out of engage-ment with said stationary element, a control member connected to said operating lever in a manner whereby the application of a force by the control member tends t0 rock the operating lever in said one direction against the pressure of said spring, said movable hook member being closed with a fast travel and low mechanical advantage as long as the torque 0n said operating lever due to the pressure of said spring exceeds the torque due to the force exerted by said control member, a-nd when the torque due to the force of said control member exceeds the torque due to said spring, said operating lever is rocked into engagement with said stationary element, giving a fulcrumed lever action on the outer end of Said arm, whereby said movable hook member is thereafter closed with a slow travel and high mechanical advantage, a link pivoted intermediate its ends on said operating lever, stops for limiting the angular movement of said link between a iirst position and a second position, a pawl connected to one end of said link and extending around to the opposite side of the pivot point thereof, an arcuate rack projecting laterally from said movable hook member, said rack being engageable by the free end of said pawl, a spring bearing against the other end of the said link and against the free end of said pawl, said last-named spring being operative to urge said free end of the pawl into engagement with said rack when said link is in said first position, and out of engagement therewith when said link is in said second position, said link being initially disposed in said first position while said movable hook member is being drawn tight on an object, whereby said pawl is ratcheted over said rack and engages one of the teeth thereof when the force exerted by said control member is relaxed, Said pawl and said link thereafter holding said operating lever in the position occupied by the latter when said control member was relaxed, whereby said movable hook member is locked in closed position, said link being moved to said second position when said control mem-ber is relaxed, whereby the next succeeding application of force by said control member causes said pawl to be lifted out of its seating engagement with said rack, allowing said last-named spring to move said pawl clear of the rack and releasing said operating lever, said operating lever being moved out of engagement with said stationary element by said first-named spring, permitting said movable hook member to open, and a cam surface on said rack engageableby said pawl as said operating lever approaches its initial position, for deecting the free end of the pawl in a direction causing said link to move to said rst position.

'7. An artificial arm hook comprising a base having a stationary hook member rigidly fixed thereto, a movable hook member pivoted on said .base for swinging movement toward and away from said stationary member, actuating means including an arm projecting radially from said movable hook member adjacent the axis of rotation thereof, an operating lever pivoted on the outer end of said arm and extending inwardly toward said axis, said operating lever having a toothed sector projecting outwardly from its pivot support, an arcuate rack mounted on said base and engageable by said toothed sector, said rack having its center of curvature on said axis of said movable hook member, a force-transmitting control member connected to said operating lever, a spring connected to said operating lever to apply a torque thereto opposing the torque exerted by said control member, said spring being operable to hold said toothed sector normally out of engagement with said arcuate rack, whereby said movable hook member is closed with a fast travel and low mechanical advantage by virtue of the direct application of force of said control member to said arm as long as the torque of said spring on said operating lever exceeds the torque of said control member thereon, and when the torque on said operating lever produced by said control member exceeds the torque produced by said spring, said toothed sector is moved into engagement with said arcuate rack, giving a fulcrumed lever action ou the outer end of said arm, whereby said movable hook member is thereafter closed with a slow travel and high mechanical advantage, a link pivoted intermediate its ends on said operating lever, stops for limiting the angular movement of said link between a rst position and a second position, a pawi connected to one end of said link and extending around to the opposite side of the pivot point thereof, another rack engageable by the free end of said pawl, a spring bearing against the other end of said link and against thev free end o said pawl, said last-named spring being operative to urge said free end of the pawl into engagement with said last-named rack when said link is in said 45 rst position, and out of engagement therewith 18 when said link is in said second position, said link being initially disposed in said rst position While said movable hook member is being drawn tight on an object, whereby said pawl is ratcheted over said last-named rack and engages one of the teeth thereof when the force exerted by said control member is relaxed, said pawl and said link thereafter holding said operating lever in the position occupied by the latter when said control member was relaxed, whereby said movable hook member is locked in closed position, said link being moved to said second position when said control member is relaxed, whereby the next succeeding application of force by said control member will lift said pawl out of its seating en gagement with said last-named rack, allowing said last-named spring to move said pawl clear of the rack and releasing said operating lever, said operating lever being then moved out of engagement with said rst-named rack by said rst-named spring, permitting said movable hook member to open, and means engageable by said pawl for moving the same in a direction to cause said link to return to said first position.

- GILBERT M. MOTIS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,398,977 Thornton Apr. 23, 1946 FOREIGN PATENTS Number Country Date 315,024 Germany Sept. 22, 1919 828,272 France Feb. 7, 1938 OTHER REFERENCES Report of European Observations, by Commission on Amputations and Prostheses, received in Div. 55 of the Patent Oflice February 12, 1947, page 126, paragraph 5; and page 21, paragraph 3, on the Hobbs hand. A 

